This invention relates, generally, to a method of forming a manifold in a substrate of a printhead substructure, and more specifically, to a method of forming a manifold in a substrate using a laser-assisted etching process and a printhead substructure having such a substrate.
A prior art ink-jet printer typically includes a printing cartridge or pen in which small droplets of ink are formed and ejected toward a printing medium. Such pens include printheads with orifice plates having very small nozzles through which the ink droplets are ejected. Adjacent to the nozzles inside the printhead are ink chambers, where ink is stored prior to ejection. Ink is delivered to the ink chambers through ink channels. A manifold in the printhead connects to the ink channels to deliver ink from an ink supply to the ink chambers. The ink supply may be contained, for example, in a reservoir part of the pen.
Ejection of an ink droplet through a nozzle may be accomplished by quickly heating a volume of ink within the adjacent ink chamber. The rapid expansion of ink vapor forces a drop of ink through the nozzle. This process is called xe2x80x9cfiring.xe2x80x9d The ink in the chamber may be heated with a transducer, such as a resistor that is aligned adjacent to the nozzle. The length of the ink channel from the manifold to a resistor is commonly known as a shelf length of the particular resistor.
During firing, ink along an ink channel is forced away from the ink chamber towards the manifold. This ink that is forced away from the ink chamber will take a finite time to flow back towards the ink chamber. This finite time determines a maximum frequency at which a pen can be fired. During printing, a pen is mounted on a carriage and transported over a medium for printing on the medium. At any one time, only a fraction of the total number of nozzles can be fired. To compensate for displacement caused by carriage movement, the nozzles are staggered on the printhead to allow the printhead to print along a straight line perpendicular to an axis of carriage movement. This staggering of nozzles often results in different shelf lengths in the printhead. A longer shelf will take a proportionately longer time to refill after firing. The longest refill time therefore limits maximum frequency of operation of a pen. There is another problem associated with a printhead of non-uniform shelf lengths. With non-uniform shelf lengths, there will be differences between refill rates for the different ink chambers. The refill rate differences result in different drop volumes or weights for the different transducers which ultimately affect print quality.
Typically, the manifold is created by sand blasting a slot through a substrate of the printhead as disclosed in U.S. Pat. No. 5,478,606. During sand blasting, a stream of compressed air and sand particles is directed at the substrate to allow the sand particles to cut a slot through the substrate to define the manifold. Due to grain size variation and moisture content of the sand particles, an opening of the manifold at a transducer-supporting side of the substrate may be off-center and has jagged edges. Such an opening exacerbates the problem caused by non-uniform shelf lengths.
Impact on the substrate caused by sand blasting may also cause cracks in the transducer side of the substrate. The cracks result in leakage of ink from the manifold.
A combination process of wet etching and sand blasting bas been considered for forming a manifold having an opening that is more accurately centered and has a regular edge. This combination process involves (1) etching a recess in the transducer-supporting side of the substrate to define the opening and (2) sand blasting from the opposite side of the substrate to cut a slot that connects to the recess. Wet etching requires development of suitable masking layers for protecting the surface of areas of the printhead which are not to be etched. These masking layers are not trivial to develop. If not properly protected, an etchant used in wet etching will also etch away portions of the printhead that are not to be etched. The combination process therefore entails great care for implementation.
According to an embodiment of the present invention, there is provided a method of forming a manifold through a substrate of a printhead substructure. The substrate has an ink reservoir-facing side and an opposing transducer-supporting side. The method includes (1) introducing an etchant that comes into contact with the transducer-supporting side of the substrate and (2) irradiating the etchant contacting side of the substrate using a laser beam. The irradiated areas of the substrate are etched to define a first portion of the manifold therein. The method further includes forming a second portion of the manifold that connects to the first portion. Preferably, forming the second portion includes sand blasting through the substrate from the ink reservoir-facing side of the substrate.
According to the embodiment of the present invention, there is provided a printhead substructure for an ink-jet pen. The substructure includes a substrate having a reservoir-facing side and an opposing transducer-supporting side. The transducer-supporting side of the substrate supports transducers. The substrate also supports a barrier layer that defines ink channels and ink chambers adjacent the transducers. A manifold is formed through the substrate for delivering ink from a reservoir through the ink channels to the ink chambers. The manifold is manufactured according to a method described above. The substructure further includes conductors for carrying electrical signals to activate the transducers.